The present invention relates to a hermetic motor-driven compressor for use in refrigerators, freezers and other low-temperature appliances.
Japanese Patent Publication No. 8-144950 discloses hermetic motor-driven compressors. An example of such conventional hermetic motor-driven compressors is disclosed in FIG. 7. Also, FIG. 8 shows a principal portion of a crankshaft of the conventional hermetic motor-driven compressor. In FIGS. 7 and 8, The hermetic motor-driven compressor includes a compression component 2 and a motor drive component 3 in a hermetically sealed enclosure 1, in which refrigerating machine oil 4 is held in the bottom of the hermetically sealed enclosure 1. Refrigerant 14 is filled in a space within the hermetically sealed enclosure 1.
Further, a crankshaft 5 connected rotatably to the motor-driven component 3 has a journal portion that is supported by a bearing 7, and the crankshaft 5 is provided with an eccentric portion 6 that is eccentric relative to the journal portion. An oil feed pipe 8 is fixedly secured to the eccentric portion 6 while the leading end of the oil feed pipe is opened in the refrigerating machine oil 4.
The eccentric portion 6 is connected to a connecting rod 9 which is connected a piston 10 of the compression portion with a piston pin 11 to compress the refrigerant.
In operation of such a hermetic motor-driven compressor, torque of the motor drive component 3 is converted to reciprocating movement through the eccentric portion 6 and the connecting rod 9 so as to perform compression by the piston 10 in the compression component 2.
The crankshaft 5 is rotatively driven by the motor drive component 3 to rotate the oil feed pipe 8 with its centrifugal pumping portion 8a dipped in the refrigerating machine oil 4 held within the hermetically sealed enclosure 1 to produce an oil pressure inside of the oil feed pipe 8, so that the refrigerating machine oil 4 can be sucked up by the oil feed pipe 8 and then supplied to every sliding portion in the compressor.
In the above-mentioned arrangement, however, since the centrifugal pumping portion 8a is rotated in a dipped manner in the refrigerating machine oil 4, the oil feed pipe 8 runs through the oil 4 while cutting the oil surface like a truncated conical contour to stir the refrigerating machine oil 4 vigorously.
Thereupon, the refrigerant 14 which has dissolved in the refrigerating machine oil 4 forms bubbles, which shake the rotating oil feed pipe 8 to generate the resonance sound. It is problematic that the resonance sound of the pipe 8 increases noise in the hermetic motor-driven compressor together with the oil surface cutting sound produced by the oil feed pipe 8 cutting into the oil surface and the colliding sounds produced by droplets, spattered from the refrigerating machine oil 4 stirred vigorously by the oil feed pipe 8, clashing against the oil surface, the inside wall of the hermetically sealed enclosure, the compression component and so on.
There is also such a problem that the noise in the hermetic motor-driven compressor is increased also by the resonance sound of the crankshaft 5 which is produced by repetition of deflection thereof caused when the crankshaft 5 is oscillated by large intermittent loads acting to the eccentric portion 6 through the connecting rod 9 at the time of compression in the compression component 2. Otherwise, if the oil feed pipe 8 is provided coaxially with the crankshaft 5, the stirring of the refrigerating machine oil may be prevented, but the centrifugal pumping action thereof may be lost, which causes problems with the oil feeding function of the compressor.
It is an object of the invention to solve the above-mentioned problem in such a way that the noise in the hermetic motor-driven compressor can be reduced by decreasing the resonance sound of the oil feed pipe, the oil surface cutting sound produced by the oil feed pipe rotated in a dipped manner in the oil, the spattering sound of the refrigerating machine oil stirred by the oil feed pipe and the resonance sound of the crankshaft caused by the deflection thereof while the lubrication for the sliding portions of the compression component can be guaranteed.
For accomplishing the above-mentioned object, the present invention contemplates the selection of a material for the oil feed pipe having a natural frequency that is a low frequency which has less influence on the sense of hearing.
Further, a configuration of the oil feed pipe is designed to have a high rigidity or to suppress the stirring of the refrigerating machine oil. Additionally, an interposition member for suppressing the resonance sound of the oil feed pipe is disposed at a joint of the oil feed pipe.
Further, the eccentric portion formed in the crankshaft is provided at its lower portion with a balance weight, and the balance weight has a coaxial oil feed pipe adapted to be rotated coaxially with the journal of the crankshaft.